Slide fastener stringer with folded and bonded continuous molded coupling element and method and apparatus for manufacturing

ABSTRACT

The leg portions of a continuous molded coupling element are bonded together to reinforce the attachment of connecting threads embedded in the leg portions.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to slide fasteners and particularly to slidefasteners employing continuous molded coupling elements joined in atrain by connecting threads as well as their methods and apparatus formanufacture.

2. Description of the Prior Art

The prior art, as exemplified in U.S. Pat. No. 3,328,857, No. 3,414,948,No. 3,445,915 and No. 3,487,531, contains a number of continuous moldedcoupling elements joined by embedded connecting threads and methods andapparatus for manufacture thereof. Generally, the connecting threads insuch prior art coupling elements are unsuitable for use as the means ofattachment to a carrier tape since the connecting threads are embeddedrelatively shallowly in the legs of the coupling elements and are easilypulled from coupling elements by cross-wise forces on the slidefastener; thus the leg portions of the prior art coupling elements aregenerally sewn to the edge of the tape. Such sewing of the leg portionsto the tapes results in increased cost and extra steps in themanufacture of the coupling elements.

SUMMARY OF THE INVENTION

The invention is summarized in a stringer for a slide fastener includinga tape, a train of molded synthetic polymer coupling elements disposedalong one longitudinal edge of the tape, each of the coupling elementshaving a head portion and a pair of leg portions which extend in thesame direction from opposite sides of the head portion, first and secondconnecting thread means having segments embedded in the respective legportions to connect the coupling elements in the train, the leg portionsbeing bonded together adjacent their heels, and securing thread meansextending around the connecting thread means between the couplingelements to secure the train of coupling elements to the one edge of thetape.

An object of the invention is to construct a slide fastener stringerhaving a continuous molded coupling element joined by connecting threadsand woven together in the edge of a tape by using present weavingtechniques.

Another object of the invention is to reinforce embedded connectingthreads joining continuous molded coupling elements in order towithstand cross-wise forces on a slide fastener.

It is also an object of the invention to weld the heels of the legportions of coupling elements together to reinforce connecting threadsjoining the coupling elements as well as to seal in an invested cordbetween the leg portions.

One feature of the invention is the formation of a groove in the joinedheels of leg portions of coupling elements to receive a longitudinalcord and improve the stability of the coupling elements relative to thetape.

Another feature of the invention is that one-half of a cord receivinggroove is formed in the heel of each leg portion during the molding ofthe slide fastener.

In still another aspect, the bending of leg portions of continuousmolded coupling elements is improved by forming notches on the inside ofhead portions of the coupling element. Other objects, advantages, andfeatures of the invention will be apparent from the followingdescription of the preferred embodiment taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a slide fastener made in accordance with theinvention.

FIG. 2 is a cross section view of a portion of one stringer of the slidefastener of FIG. 1.

FIG. 3 is a side view of a molded coupling element during anintermediate step of forming a coupling element for the stringer of FIG.1.

FIG. 4 is a front view of a portion of an apparatus for continuouslymolding a train of the coupling elements of FIG. 3.

FIG. 5 is a side cross section view of the molding apparatus of FIG. 4.

FIG. 6 is an enlarged view of a portion of the cross section view ofFIG. 5.

FIG 7. is a front view of an apparatus for bonding leg portions of thecoupling elements of FIG. 2 together.

DESCRIPTION OF THE PREFERRED EMBODIMENT

A slide fastener, shown in FIG. 1 and manufactured in accordance withthe invention, includes a pair of carrier tapes indicated generally at10 and 12 and a pair of trains of coupling elements indicated generallyat 14 and 16 secured to the inner edges of the respective tapes 10 and12. A slider 18 is slidably mounted on the coupling elements 14 and 16for opening and closing the slide fastener. The tape 10 and couplingelements 14 form a left stringer while the tape 12 and the couplingelements 16 form a right stringer; the left and right stringers togetherforming a chain for the slide fastener. The right stringer issubstantially identical to the left stringer except that it is a mirrorimage thereof.

Each of the coupling elements 14 as illustrated in FIG. 2 has a headportion 20 with a pair of leg portions 22 and 24 extending in the samedirection from opposite sides of the head portion 20. Four connectingthreads 26, 28, 30 and 32 are embedded in the leg portions 22 and 24near converging inside surfaces thereof; one pair of the connectingthreads 26 and 28 being embedded in the respective leg portions 22 and24 adjacent to the heels thereof while the other pair 30 and 32 areembedded in the respective leg portions 22 and 24 at a location spacedtoward the head portion 20 from the pair of threads 26 and 28. Aninvested cord 34 is positioned between the leg portions 22 and 24 whichare bonded or sealed together, such as by a weld 36, formed adjacent tothe heels of the leg portions 22 and 24. Well or groove halves 38 and39, together forming a single groove indicated generally at 37, areformed in the heels of the prospective leg portions 22 and 24 toaccommodate a support cord 40. The tape 10 has a plurality of warpthreads 42 with an interwoven weft thread 44 which encircles the supportcord 40 together with the connecting threads 26, 28, 30 and 32 and theinvested cord 34 between the coupling elements 24 to secure the train ofcoupling elements 14 to the inner edge of the tape 10.

The bond 36 formed between the leg portions 22 and 24 adjacent the heelthereof substantially increases the strength of the attachment of thecoupling elements 14 to the tape 10. The connecting threads 26, 28, 30and 32, being only shallowly embedded in the coupling elements 14 on theinside of the leg portions 22 and 24, have a tendency to be pulled fromthe coupling elements 14 in absence of the bond 36; but the bond 36joins inside surfaces of the leg portions 22 and 24 together to form aunitary heel portion with the connecting threads, particularly threads26 and 28, centrally embedded therein, to greatly reinforce the union ofthe connecting threads 26, 28, 30 and 32 with the leg portions 22 and24. Also, the bond 36 seals in the invested cord 34 capturing it betweenthe leg portions 22 and 24. By so capturing the invested cord 34, itreinforces the union of the connecting threads, particularly the threads30 and 32, due to compression between the leg portions 22 and 24adjacent the threads 30 and 32; the invested cord 34 also provides anadditional member of relatively greater strength to help withstandcrosswise slide fastener forces transmitted through picks of the weftthread 44. Being located between the connecting threads 30 and 32 aswell as absorbing a substantial share of the tension forces of the weftthread picks, the invested cord 34 maintains spacing between the threads30 and 32 and decreases distortion of the spacing between couplingelements due to pulling of the weft thread picks on the threads 30 and32.

The groove 37 with the support cord 40 being laid therein greatlyimproves the stability of the coupling elements 14 and their attachmentto the tape 10. In addition to greatly increasing the longtudinalstrength and stability of the inner edge of the tape 10, the cord 40 inthe groove 37 prevents the elements 14 from moving sideways relative tothe tape 10. The support cord 40 together with the invested cord 34 andthe connecting threads 26, 28, 30 and 32 form a substantial packageintegrally joined with the leg portions 22 and 24 of the couplingelements 14 for attachment by the encirclement of the weft thread 44 onthe inner edge of the tape 10.

An apparatus, shown in FIGS. 4, 5 and 6, for continuously molding thecoupling elements 14 in an elongated, flat and unfolded condition, asshown in FIG. 3, includes a rotatable cavity wheel 50 having a pluralityof spaced elongated cavities 52 formed in a row around the peripherythereof. The cavities 52 extend parallel to the axis of the wheel 50. Aplurality of annular grooves 54, 56, 58 and 60 are formed in theperiphery of the wheel 50 for receiving the respective connectingthreads 26, 28, 30 and 32 to intersect end or leg forming portions ofthe cavities 52. Slidingly engaging the periphery of the wheel 50, astationary injection shoe 62 has a passageway 66 communicating between amolten thermoplastic injection means and the cavities 52 as the cavitywheel 54 is rotated. Also, the shoe 62 has a V-shaped projecting rib 68mating with a V-shaped annular groove 70 formed in the periphery of thewheel 50 and intersecting head forming portions of the cavities 52 forforming notches 42, FIG. 3, in the coupling elements 14. Sides of therib 68 extend into the leg forming portions of the cavities 52 adjacentto the head forming portion. Projecting ribs 72 and 74 on the shoe 62mate with annular grooves or channels 76 and 78 formed in the peripheryof the wheel 50 and intersecting the outer edges or heels of the legforming portions of the cavities 52 for forming the groove halves 38 and39 in the heels of the leg portions 22 and 24 of the coupling elements14.

An apparatus for welding the leg portions 22 and 24 of the couplingelements 14 together after insertion of the invested cord 34 isillustrated in FIG. 7. A rotatable wheel 80 is notched with a spacingcoinciding with the proper spacing of elements 14 to receive thecoupling elements 14 bent into a U-shape. Suitably disposed above thewheel 80 is a smaller wheel 82 rotatably mounted on the lower end of anultrasonic vibration mechanism 84, for further bending and welding theleg portions 22 and 24 together.

In the method of manufacture of the left stringer for the slidefastener, the coupling elements are initially molded in the apparatus ofFIGS. 4, 5 and 6 by injecting molten synthetic polymer resin through thepassage 66 into the cavities 52 as the cavities 52 are moved beneath theshoe 62. The connecting threads 26, 28, 30 and 32 fed into therespecting grooves 54, 56, 58 and 60 of the cavity wheel 50 beneath theshoe 62 became embedded in the injected polymer resin. After hardening,the train of coupling elements 14, in the flat unfolded condition ofFIG. 3 and joined in a train by the connecting threads 26, 28, 30 and32, are stripped or removed from the cavity wheel 50. The groove halves38 and 39 and the V-shaped groove 42 are formed by the respective ribs72, 74 and 68 during the formation of the trains of unfolded couplingelements.

Subsequently, the coupling elements 14 are suitably folded into aU-shape with the leg portions 22 and 24 extending in the same direction,the cord 34 is inserted between the leg portions 22 and 24, and thetrain of coupling elements 14 with the invested cord 34 is fed to theperiphery of the wheel 80, FIG. 7. Ultrasonic energy from the wheel 82welds the leg portions 22 and 24 together at 36 as shown in FIG. 2; thewelding also forming the grooves 37 from the halves 38 and 39. The trainof coupling elements 14 with the sealed leg portions is fed to aconventional slide fastener weaving apparatus along with the cord 40which is laid in the grooves 37. The weft thread 44 is woven with thewarp threads 42 and is passed around the package of cords 34 and 40 andthreads 26, 28, 30 and 32 between the coupling elements 14 to form awoven slide fastener stringer.

Folding of the leg portions 22 and 24 is aided by the V-shape grooves42. The sides of the grooves 42 extending into the leg portions 22 and24 narrows the junctions of the leg portions with the head portion 20making such junctions more flexible and easier to bend.

Forming the grooves 37 by forming the two groove halves in the heels ofthe respective leg portions 22 and 24 as they are molded avoids extrasteps in manufacturing the coupling elements. Additionally distortion,such as would be caused by plastically deforming the heels of the legportions after they have been bonded together, is avoided; thusproducing coupling elements with uniform dimensions.

Since many modifications, variations and changes in detail may be madeto the described slide fastener and its method and apparatus formanufacture it is intended that all matter in the foregoing descriptionand shown in the accompanying drawings be interpreted as illustrativeand not in a limiting sense.

What is claimed is:
 1. A stringer for a slide fastener comprisinga tape,a train of molded synthetic polymer coupling elements disposed along onelongitudinal edge of the tape, each of said coupling elements having ahead portion and a pair of leg portions which extend in the samedirecton from opposite sides of the head portion, said leg portionsterminating in heels thereof opposite to the head portions, first andsecond connecting thread means having segments embedded in therespective leg portions to connect the coupling elements in the train,said leg portions being bonded together adjacent their heels, securingthread means extending around the connecting thread means between thecoupling elements to secure the train of coupling elements to the oneedge of the tape, said coupling elements each including a groove formedin the joined heels of the leg portions, said grooves extendinglongitudinal to the tape, and a support cord in the one edge of the tapelaying in the grooves of the coupling elements.
 2. A stringer for aslide fastener comprisinga tape, a train of molded synthetic polymercoupling elements disposed along one longitudinal edge of the tape, eachof said coupling elements having a head portion and a pair of legportions which extend in the same direction from opposite sides of thehead portion, said leg portions terminating in heels thereof opposite tothe head portions, first and second connecting thread means havingsegments embedded in the respective leg portions to connect the couplingelements in the train, said leg portions being bonded together adjacenttheir heels, an invested cord between the leg portions, securing threadmeans extending around the connecting thread means and the invested cordbetween the coupling elements to secure the train of coupling elementsto the one edge of the tape, said coupling elements each including agroove formed in the joined heels of the leg portions, said groovesextending longitudinal to the tape, and a support cord in the one edgeof the tape laying in the grooves of the coupling elements.